Welding Tips and Tricks

I recently picked up a used Miller 200DX I couldn't resist and have been running it through its paces over that past month. The fan on demand feature appears to be working perfectly along with everything else, and I was wondering if the fan kicks on when I am approaching an overheat and shut down situation or if it kicks on at a temp well below that. I am aware of the rather low duty cycle of the 200DX, and I do mix in helium to help reduce my running amperage. Regardless, I't would also be nice to have some idea how much time I have after the fan kick on before I need to give the welder a break. Anyone have a feel for that? My prior experience has only been with continuous fan tig welders. Thanks

I guess the way to get the "true" answer would be to give Miller a ring. They have been very helpful when I have called over the years. That said, I can relate my experience with my 200DX and my Hypertherm plasma cutter both of which have fan on demand. On both machines the fan starts to run shortly after I strike an arc. It would not make a lot of sense to wait until the machine was almost overheated to start the cooling fan. I would think of it as a "no demand, no fan" feature. It basically shuts off the fan when not needed to save (a little bit of) energy and cut down on noise.

As far as when to give the machine a break... you need to look at the duty cycle chart in the manual. If the duty cycle for the amperage you are welding at is 40% you can burn for 4 minutes out of 10. 4 minutes on and 6 minutes off. remember that duty cycle is generally specified with reference to a 10 minute period. 8 on and 12 off will not do the trick.

Ken

We run those machines a lot. And lots of different kinds of the millers at work. The fan will run a lot if your working the machine but you don't have to worry about tripping it out. The thermal limits inside it are set to shut it off before you damage it. I've tripped them a few times but they were extreme situations. I.E. In a room where it was 130 deg and I as running close to the max the machine was rated for putting out. And I went about 6 hours before it tripped. It was an emergency repair so it was running almost continuos.